Field of the Invention
The present invention relates to an image capturing apparatus and a method of controlling the same.
Description of the Related Art
Image sensors used in image capturing apparatuses such as digital still cameras or digital video cameras are highly multi-functionalized. For example, some image sensors are known as sensors each having a focus detection function. Japanese Patent Laid-Open No. 2001-124984 discloses a technique for allowing focus detection of a phase difference detection method using output signals from two photodiodes which are arranged together with one microlens in one pixel of the image sensor and receive light beams passing through different pupil areas of an imaging lens. When the output signals from the two photodiodes in a single pixel are added, an image output can be obtained. With this arrangement, the signals must be obtained from the two photodiodes for each pixel. As compared with a conventional arrangement in which one photodiode is arranged for one pixel, the readout time is undesirably doubled. However, the readout time needs to be shortened to achieve readout operation at a predetermined frame rate.
The present invention provides an image capturing apparatus capable of shortening the signal readout time in the image capturing apparatus using an image sensor capable of performing focus detection of a phase difference detection method in consideration of the above problem.